After talking to hundreds of people over the years about glucosamine is this:

There are those for whom it just does not work, or is not needed.

Then there are those who swear it is terrific.

Since glucosamine is made in your body from the glutamine chemistry, it
is dependent on glutamine intake. There are many enzymes involved with this
system, and if any one of them is faulty, then the glucosamine synthesis fails.
I suspect that people vary in their need for it, and those who do not make
it well for themselves, do well on supplements. Those who have enough, don't need more.

I've posted that chemistry many times on both boards...so I won't post it here.
Glutathione in the liver is also made from l-glutamine.

For me SAMe has been the exact opposite. Now that does work for me!

BTW Cosamin DS had a very big problem in the not too recent past. Its glucosamine product was
contaminated with high levels of manganese. This has been fixed...but I don't think they are
so terrific to have not been careful in the first place.